Magneto-optical Devices for Optical Integrated Circuits

16

Magneto-optical Devices for Optical Integrated Circuits

Vadym Zayets and Koji Ando Nanoelectronics Research Institute National Institute of

Advanced Industrial Science and Technology (AIST) Japan

1 Introduction

Magneto-optical materials have two unique properties which make them important for a variety of optical applications The first property is non-reciprocity The time inverse symmetry is broken in magneto-optical materials Therefore properties of magneto-optical materials are different for two opposite directions of light propagation and optical non-reciprocal devices like the optical isolator and the optical circulator can be fabricated only by utilizing magneto-optical materials The second important property of the magneto-optical materials is a memory function If the material is ferromagnetic the data can be memorized by means of two opposite directions of the residual magnetization Both the reading and writing of such memory can be done by magneto-optical effect The optical isolator is an important component of optical networks It is transparent in one direction and blocks light in opposite direction Due to the imperfect matching between optical components in the network the unwanted back reflection always exists and it severely disturbs the network performance To avoid this the optical components have to be protected by an optical isolator Also the isolator is important to cut the back-travelling amplified spontaneous emission in the case of serially-connected amplifiers Today there is a big demand to integrate all optical components into an opto-electronics chip In fact the isolator is one of few components which have not yet been integrated into commercial chips It is because of difficulties to integrate magneto-optical materials into a semiconductor-made chip To solve this we proposed to use (CdMn)Te as a magneto-optical material for such isolator The (CdMn)Te exhibits a huge Faraday effect and can be grown on a semiconductor substrate For (CdMn)Te waveguide grown on GaAs substrate we achieved a high Faraday rotation of 2000 degcm a high isolation ratio of 27 dB a low optical loss of 05 dBcm and a high magneto-optical figure-of-merit of 2000 degdBkG in a wide 25-nm wavelength range (Debnath et al 2007) These values meet or exceed similar values of commercial discrete isolators We predicted theoretically (Zaets amp Ando 1999) and proved experimentally (Zayets amp Ando 2005) the effect of non-reciprocal loss in hybrid semiconductorferromagnetic metal waveguides This effect can be utilized for new designs of waveguide optical isolator Because the structure of this isolator is similar to that of laser diode such a design is beneficial for the integration The bistable laser diode with non-reciprocal amplifier was proposed to be used for high-speed optical logic (Zayets amp Ando 2001)

Source Frontiers in Guided Wave Optics and Optoelectronics Book edited by Bishnu Pal ISBN 978-953-7619-82-4 pp 674 February 2010 INTECH Croatia downloaded from SCIYOCOM

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We proposed the non-volatile high-speed optical memory which utilizes the magnetization reversal of nanomagnet by spin-polarized photo-excited electrons It was demonstrated experimentally that one selected pulse from a train of two optical data pulses with interval of 450 fs can solely excite the spin-polarized electrons without a disturbance from the unselected optical data pulse (Zayets amp Ando 2009) This proves feasibility for proposed memory to record data train with rate of 22 TBitsec

2 Cd1-xMnxTe waveguide optical isolator

The conventional bulk-type optical isolator consists of a 45-degree Faraday rotator placed between two polarizers [Fig1] The angle between axes of entrance polarizer and exit polarizer is 45 degrees In forward direction the polarization of light is 45 degree rotated by the Faraday rotator to be along the axis of the exit polarizer Therefore the light can pass through the isolator in forward direction In backward direction the direction of polarization rotation is opposite to that in forward direction due the non-reciprocal nature of the magneto-optical effect At the entrance polarizer the polarization is 90 degrees to the polarizer axis and the light is fully blocked

45deg45deg 45deg45deg

45deg45deg45deg45deg90deg

0deg0deg

Fig 1 Design of free-space optical isolator The Faraday rotator is placed between entrance polarizer (left side) and exit polarizer (right side) Upper diagrams show polarization in forward direction Lower diagrams show polarization in backward direction

In present optical networks ferrimagnetic garnet oxide crystals such as Y3Fe5O12 (YIG) and (GdBi)3Fe5Ob are used as magneto-optical materials for discrete optical isolators Because most of the active optical elements (such as the laser diode optical amplifier modulator and optical gate) are produced on GaAs or InP substrates it is desirable to integrate monolithically all optical components on these types of substrate but integration of the isolator is a difficult task Waveguide optical isolator based on the garnet film has been reported (Ando et al 1988) But the garnet-made isolators have not been monolithically integrated with semiconductor optoelectronic devices because these oxide crystals can not be grown on semiconductor substrates Paramagnetic semiconductor Cd1-xMnxTe is promising as a magneto-optical material for integrated optical isolators and circulators Cd1-xMnxTe shares the zinc-blende crystal structure with the typical semiconductor optoelectronic materials such as GaAs and InP thus its film can be grown directly on GaAs and InP substrates Cd1-xMnxTe also exhibits a huge Faraday effect (its Verdet constant is typically 50-200 degcmkG) (Furdyna 1988) near its absorption edge because of the anomalously strong exchange interaction between the sp-band electrons and the localized d-electrons of Mn2+ Furthermore the tunability of its absorption edge from 156 to 21 eV with Mn concentration makes the Cd1-xMnxTe magneto-optical waveguide compatible with (AlGaIn)PGaAs optoelectronic devices operating in the wavelength range of 600-800 nm For longer-wavelength (λ=800-1600 nm)

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optoelectronic devices Cd1-x-yMnxHgyTe can be used Bulk optical isolators using these materials are now commercially available (Onodera et al 1994)

Laserbeam

GaPprism

Polarizer

GaAs

Cd Mn Te1-x x

TV-CAMERAH

Fig 2 Experimental set-up to evaluate magneto-optical TE-TM waveguide mode conversion

For the Cd1-xMnxTe to be used as a material for the waveguide isolator several conditions should be satisfied For a practical Cd1-xMnxTe waveguide isolator the isolation ratio should exceed 20 dB insertion loss should be below 1 dB and operation wavelength range should be wider than 20 nm This performance can only be achieved with a magneto-optical waveguide having a mode conversion ratio above 95 and a figure-of-merit above 100 degdB Below we will show that using advanced waveguide structure and optimized fabrication technique this conditions can be achieved in Cd1-xMnxTe waveguide grown on GaAs substrate The Cd1-xMnxTe has about 12 lattice mismatch with GaAs The growth conditions of Cd1-

xMnxTe on GaAs substrate should be well optimized Otherwise the high density of dislocation in Cd1-xMnxTe film causes high optical loss in Cd1-xMnxTe waveguide (Zaets et al1997) and low value of Faraday rotation The Cd1-xMnxTe waveguide was grown by molecular beam epitaxy (MBE) on GaAs (001) substrate We optimized the growth conditions and fabricated the Cd1-xMnxTe waveguide in the following way In the beginning GaAs substrate was thermally cleaned at 4000 C under atomic hydrogen flux to remove oxides from GaAs surface Before initiating the growth the GaAs substrate was kept for 30 minutes under Zn flux to prevent the formation of the undesired Ga2Te3 compound At first a thin 10 nm ZnTe film was grown on the GaAs substrate to initialize the (001) growth Following a 1-microm thick CdTe buffer layer Cd1-xMnxTe waveguide was grown It consists of a 3-microm-thick Cd073Mn027Te waveguide cladding and a 1-microm-thick Cd077Mn023Te waveguide core The waveguide core was sandwiched between two 500-nm-thick Cd1-

xMnxTe (x=027-023) graded-refractive-index clad layers for which the Mn concentration was changed linearly with thickness We used the Cd073Mn027Te layer as a cladding layer since GaAs is an optical absorber with a higher refractive index than that of Cd1-xMnxTe a single Cd1-xMnxTe layer on GaAs does not work as a waveguide One needs transparent cladding layers with smaller refractive index Cd073Mn027Te satisfies these conditions because Cd1-xMnxTe with higher Mn concentration has a smaller refractive index and wider optical band gap The graded-refractive-index clad layers are essential for Cd1-xMnxTe waveguide to achieve high magneto-optical TE-TM waveguide mode conversion and high optical isolation Figure 2 illustrates the experimental setup for evaluating optical propagation loss and TE-TM waveguide mode conversion (Zaets amp Ando 2000) A GaP prism was used to couple the laser light from tunable Tisapphire laser (λ=680 -800 nm) into a Cd1-xMnxTe waveguide A cooled CCD TV-camera collected light scattered normally from the film surface A linear polarizer was placed in front of the TV camera with its polarization axis perpendicular to

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the light propagation direction With this configuration only the TE mode component of waveguiding light can be detected by the high-sensitivity TV camera In the absence of a magnetic field a scattered light streak was seen when the TE mode was excited (Fig 3(a)) but it was not seen when TM mode was excited (Fig 3 (b)) Also weak dot-like scattering on defects was seen in both cases

TM

TE

H=0 H=5 kGauss H=5 kGaussa)

b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

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Nor

mol

azed

int

ensi

ty

Propagation distance mm

0

25

50

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mol

azed

int

ensi

ty

TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

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50

75

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Nor

mol

azed

int

ensi

ty


0

25

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Nor

mol

azed

int

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ty

Fig 3 TM-TE mode conversion ratio in Cd1-xMnxTe waveguide at λ=730 nm (Zayets amp Ando 2004)

For the evaluation of the magneto-optical TE-TM waveguide mode conversion a magnetic field was applied in parallel to the light propagation direction A light streak with a periodically modulated intensity was observed for both TE mode excitation (Fig 3 (c)) and TM mode excitation (Fig 3 (d)) Figures 3 (e)-(f) show the measured intensity of the modulated streak along the propagation length The intensity was normalized to input intensity The oscillations maxima in the case of TE excitation (Fig 3 (e)) correspond to the oscillations minima in the case of TM excitation (Fig 3 (f)) and vice versa Under an applied magnetic field the polarization of the waveguide mode rotates because of Faraday effect If the TE-TM mode phase mismatch is not zero the eigenmodes of the waveguide are elliptically polarized and the rotation between TE and TM polarizations is not complete As seen from Figs 3 (c)- 3 (f) the Cd1-xMnxTe waveguide with the graded index cladding layer shows almost complete mode conversion The Cd1-xMnxTe waveguide with graded buffer layers has low optical loss high TE-TM mode conversion efficiency (more than 98 ) and high isolation ratio (more than 20 dB) However high isolation ratio was obtained in narrow about 3 nm wavelength range For practical application of the isolator the operation wavelength range should be at least 20 nm For the operation of the optical isolator the rotational angle of Faraday rotator should be 450 (Fig1) for any operational wavelength Cd1-xMnxTe is a diluted magnetic semiconductor It has a high value of Faraday rotation but it is high only near its bandgap and near the bandgap the dispersion of Faraday rotation is significant as well Of course Cd1-xMnxTe is a paramagnetic material and at each wavelength the Faraday rotation can be tuned to 450 by the changing magnetic field However such tuning is not practical for real applications because a practical isolator needs a permanent magnet with a fixed magnetic field Below we will show that it is possible to achieve practically dispersion-free Faraday rotation in

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wide wavelength range by combining in a waveguide Cd1-xMnxTe bulk material and a Cd1-xMnxTe quantum well (QW) The Faraday effect in a Cd1-xMnxTe QW is greater than that of bulk Cd1-xMnxTe and it is not as dependent on wavelength However due to the two-dimensional nature of the QW its optical properties become significantly different for light polarized in the plane of the QW and perpendicular to the QW Therefore for a waveguide composed of only a single QW there is a big difference between propagation constants of TE and TM modes Due to TE-TM mode phase mismatch the linearly polarized light can be easily converted to elliptically polarized light which reduces the performance of the isolator Therefore a waveguide composed of only a single QW cannot be used for the isolator application In order to make a high performance isolator we need a large wavelength independent Faraday effect and small phase mismatch between TE and TM modes For that purpose we proposed using an optical waveguide that combines Cd1-xMnxTe bulk material and a single QW (Debnath etal 2004) Figure 4 shows the (CdMn)Te(CdZn)Te QW waveguide structure There are two buffer layers of ZnTe (10 nm) and CdTe (1 microm) and a Cd071Mn029Te (3 microm) waveguide clad layer The waveguide core layer was sandwiched between two Cd1-xMnxTe (05 microm) graded layers in order to reduce TE-TM mode phase mismatch The waveguide core consists of a Cd076 Mn02TeCd075Zn025 Te single QW and a 1-microm-thick Cd 075 Mn 025 Te layer where thickness of the Cd076 Mn024Te well varies between 20ndash100 Aring and the thickness of Cd075Zn025Te barrier is 100 Aring

Substrate GaAs (001)

Buffer ZnTe (10 nm)

Buffer CdTe (1 μ m)

Clad Cd071Mn029Te (3 μ m)

Barrier Cd075Zn025Te (100 )

Graded Cd1-xMnxTe (x=029-025)

Well Cd076Mn024Te (20 -100 )Barrier Cd075Zn025Te (100 )

Cd075Mn025Te (1 μ m)


Co

re

Fig 4 Structure of a (CdMn)Te waveguide with (CdMn)Te(CdZn)Te QW The waveguiding light intensity distribution is shown in the right side (Debnath et al 2007)

Figure 5 shows a spatially modulated light streak of the waveguide mode at two different wavelengths (760 and 785 nm) for the waveguides with QW and without QW The high contrast between the minima and maxima of the light intensity oscillations shows that complete mode conversion is attained for both waveguides The distance between peaks corresponds to 180 degrees of the rotation For the waveguide without QW [Figs 5 (c) and 5 (d)] there is a big difference of the rotational period for these two wavelengths However for the waveguide with QW [Figs 5(a) and 5 (b)] there was no such difference This means that for the waveguide with QW the Faraday rotation at these two wavelengths is the same Also for the waveguide with QW the oscillation period is much shorter than that of

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the waveguide without QW This corresponds to the larger Faraday rotation in the waveguide with QW

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

Fig 5 Spatially modulated light streak from waveguide TE mode for CdMnTe waveguide with QW (a) (b) and waveguide without QW (c) (d) at λ = 760 nm (a) (c) and λ = 785 nm (b) (d) under magnetic field of 55 kG (Debnath et al 2007)

Figure 6 compares the Faraday effect in Cd1-xMnxTe waveguide with QW and without QW at H=55 kG In the case of the waveguide with QW the Faraday rotation is very high (~1800 degcm) and it is almost constant in a wide wavelength range Figure 7 shows the wavelength range within which more than 95 conversion efficiency was obtained for the waveguide with single QW as a function of well width For well widths of 20ndash40 Aring the operational wavelength range is as wide as 25-nm However for thicker well widths of 70ndash100 Aring the operational wavelength range sharply decreases Analysis shows that the expansion of the wavelength range for thinner QW waveguides was due to the reduction of the mode phase mismatch to as low as 50 degcm whereas this value rose to more than 500 degcm for thicker QW waveguides Thinner QW waveguides have high Faraday rotation (asymp 2000 degcm) and small phase mismatch (asymp 50 degcm) This is the reason why thinner QW waveguides provided a wider operational wavelength range of complete mode conversion From this result we conclude that for the practical optical isolator application only waveguides with a single QW thinner than 40 Aring can be used

740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW

Fig 6 Faraday rotation in Cd1-xMnxTe waveguide with QW and without QW (Debnath et al 2007)

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0 25 50 75 1000

5

10

15

20

25

30mode conversion 100

Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio

Quantum well width (Aring)

Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB

Fig 7 Wavelength range within which the complete mode conversion is obtained as a function of QW width Inset shows the isolation ratio (Debnath et al 2004)

For an integrated optical isolator the CdMnTe magneto-optical waveguide has to be integrated with a reciprocal polarization rotator and a polarizing beam splitter Both these components can be fabricated utilizing passive optical waveguides The material of the waveguides is not essential for the operation of these components Therefore it is better to use the same passive waveguides as utilized for optical interconnection in a photonic circuit where the isolator should be integrated Figure 8 shows an example of a waveguide-type reciprocal polarization rotator It is a passive optical waveguide in which the top is cut at an angle of 45 degrees TM and TE modes are not eigenmodes in this waveguide Therefore there is a conversion between TM and TE mode along mode propagation The length of this waveguide can be adjusted to achieve the desirable angle of polarization rotation The waveguide type reciprocal polarization rotators were demonstrated utilizing Si waveguide (Brooks et al 2006] AlGaAs waveguides (Huang et al 2000) and GaInAsPInP waveguides (Kim et al 2009) Figure 11 shows an example of a waveguide-type polarizing beam splitter It is a 2x2 waveguide splitter In any waveguide splitter the coupling efficiency between an input ports and an output ports depends on the value of mode propagation constant Generally in an optical waveguide the propagation constants of TM and TE modes are different Therefore it is possible to adjust the splitter so that the TM mode couples from port 1 into port 4 and the TE mode couples from port 1 into port 3 The waveguide-type polarizing beam splitters were demonstrated utilizing Si waveguide (Fukuda et al 2006) and InGaAsPndashInP waveguides (Augustin et al 2007)

reciprocalrotator

Fig 8 Waveguide-type reciprocal polarization rotator

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TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2

Fig 9 Waveguide-type polarization beam splitter

Figure 10 shows the design of a waveguide-type polarization-independent optical isolator It consists of two polarizing beam splitters connected by two arms Each arm consists of an 45-degree reciprocal rotator and a 45-degree Cd1-xMnxTe -made Faraday rotator There is an optical absorber at port 2 to absorb backward travelling light In the forward direction the direction of polarization rotation in the Faraday rotator is the same as that in the reciprocal rotator and the total rotation angle by the reciprocal rotator and the Faraday rotator is 90 degrees The light of both polarizations propagates through the isolator from input 1 port to output port 3 In the backward direction the direction of polarization rotation in the Faraday rotator is opposite to that in the reciprocal rotator due to the non-reciprocal nature of the Faraday rotator In this case the total rotation angle is zero The light propagates from output port 3 to the port 2 where there is an absorber Therefore the input port 1 is isolated The optical paths for each polarization are shown in Fig 10 A waveguide-type polarization-independent optical circulator can be fabricated utilizing the same design In this case the correspondence between the input and output ports is port 1-gt port 3 port 2 ndashgtport 4 port 3 -gt port 2 port 4 -gt port 1

TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE

45 degreeCdMnTeFaradayrotator

input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator

Fig 10 Polarization-independent waveguide-type optical isolator circulator Polarization transformations for both propagation directions are shown

In conclusion the high performance of Cd1-xMnxTe waveguide isolator grown on GaAs substrate was demonstrated Complete TE-TM mode conversion a high Faraday rotation of 2000 degcm a high isolation ratio of 27 dB a low optical loss of 05 dBcm and a high magneto-optical figure-of-merit of 2000 degdBkG were achieved in a wide 25-nm wavelength range These values are comparable or better to that of commercial discrete isolators The propagation of waveguide mode in Cd1-xMnxTe waveguide is very similar to the light propagation in magneto-optical bulk media Therefore non-reciprocal elements such as an optical isolator circulator and polarization independent isolator can be fabricated by Cd1-xMnxTe waveguides using a similar scheme as is used for free space components Therefore using Cd1-xMnxTe all these components can be integrated with semiconductors optoelectronical components

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3 Ferromagnetic metalsemiconductor hybrid isolator

Both types of isolators either made of Cd1-xMnxTe or made of garnets required high-crystal quality materials in order to have a low optical loss and a high value of Faraday rotation In the case of Cd1-xMnxTe the magneto-optical film can be directly grown on a semiconductor substrate The defect density in Cd1-xMnxTe film should be kept low until the end of the microfabrication process For the fabrication of integrated optical circuits it is more convenient to use common fabrication technique like sputtering e-beam evaporation and lift-off Ferromagnetic metals like Fe Co or Ni are very attractive for this purpose They have high magneto-optical constants and the microfabrication of these metals is simple and well established for optoelectronic integrated circuits For example Cr and Co is often used as a metal for Ohmic contact to p-GaAs and p-InGaAs We predicted theoretically (Zaets amp Ando 1999) and proved experimentally (Zaets amp Ando 2005) the effect of non-reciprocal loss in hybrid semiconductorferromagnetic metal waveguides This effect can be use for a new design of waveguide optical isolator For this design the magnetization of the ferromagnetic metal was perpendicular to the light propagation direction and lay in the film plane (Voigt configuration) In this case a large difference exists in values of lossgain for TM modes propagating in opposite directions Thus an amplifier covered by a ferromagnetic metal can itself function as an optical isolator This ferromagnetic-metal semiconductor hybrid isolator can be beneficial for monolithic integration of the optical isolator with semiconductor optoelectronic devices because its structure is very similar to the structure of a laser diode and its fabrication process is almost the same as that of a laser diode Therefore the isolator can be integrated utilizing the present technology for a semiconductor laser diode and a semiconductor amplifier The effect of the non-reciprocal loss is unique for the hybrid waveguides In the case of the light propagation in a bulk MO material the non-reciprocal effect (variation of optical properties for opposite directions of light propagation) occurs only when the magnetization of the material is parallel to the light propagation (Faraday effect and magnetic circular dichroism) There is no non-reciprocal effect if the light propagates perpendicularly to the magnetization On the contrary in a MO waveguide even if the magnetization is perpendicular to the light propagation direction and lies in the film plane the TM mode has a non-reciprocal change of the propagation constant Figure 11 compares the magneto-optical effect in a bulk material and in an optical waveguide covered by ferromagnetic metal In the bulk material when the light propagates along magnetic field there are two magneto-optical effects magnetic circular dichroism (MCD) and Faraday effect In magnetic materials the spin-up and spin-down bands are split along the magnetic field Due to the conservation law of the time inverse symmetry the light of the left circular polarization interacts only with the spin-up band and the light of the right circular polarization interacts only with the spin-down band (In general the light of elliptical polarization interacts solely with one spin band) Therefore there is a difference of refractive index (Faraday effect) and of absorption (MCD effect) for the left and right circular polarizations when the light propagates along the magnetic field When the magnetic field is perpendicular to the light propagation there is no linear magneto-optical effect The case of a waveguide covered by magnetic metal is different Inside of the metal the optical field is evanescent As it will be shown below in the case of evanescent field the polarization rotates in xz-plane perpendicularly to the waveguide mode propagation direction (Fig 11) even without magnetic field or anisotropy Therefore if the magnetic field

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is applied perpendicularly to the waveguide mode propagation direction since the polarization of the optical field is elliptical along this direction there are MCD and Faraday effects Both these effects contribute to the non-reciprocal loss

k

E

M

EM

k

x

z

y

x

z

yrotation in xy plane

rotation in xz plane

metal

core

TM mode

a)b)

Fig 11 Magneto-optical effect a) in bulk b) in waveguide covered by ferromagnetic metal

The field of an electromagnetic wave is transverse That means that the electrical field of the wave is always perpendicular to the wave vector In the case of the light propagation in the bulk along z axis the electrical field can be described as

( )~ zi k z t

E e c cωminus +f

and 0zE = (1)

For circular polarized wave the polarization which rotates in xy-plane can be described as

x

y

Ei

E= plusmn (2)

where + and ndash correspond to the right and left circular polarized waves Next let us consider the waveguide covered by a magnetic metal The electrical field in the metal can be described as

( ) ( )~ x z x zk x i k z t i ik x k z t

E e c c e c cω ωminus + minus + minus+ = +f

(3)

Since the electrical field of the electromagnetic wave is transverse k Eperpf f for the TM mode

( 0yE = ) we have

0x x z zik E k E+ = or

x z

z x

E ki

E k= (4)

Comparing Eq 4 and Eq 2 it can be clearly seen that optical field in the metal is elliptically polarized and the polarization rotates in the xz-plane Also from Eq (4) it can be seen that the ellipticity changes polarity for opposite directions of mode propagation (kz -gt -kz) Therefore if the magnetization of the metal is along the y-direction the absorption will be different for two opposite mode propagation directions due to MCD effect Also the Faraday effect contributes to the non-reciprocal loss in waveguide Due to the Faraday

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effect the effective refractive index of the metal is different for the left and right circular polarizations The absorption by the metal is directly proportional to the amount of light inside the metal and this in turn depends on the difference of refractive indexes between the metal and the waveguide core If there is a change of refractive index due to the Faraday effect it causes the change of optical absorption of waveguide mode by the metal The effect of non-reciprocal loss has another simple explanation The propagation of waveguide mode can be considered as a plane wave which propagates in the waveguide core and experiences multi reflections from boundaries of waveguide If the magnetization of the metal is perpendicular to the plane of reflection the plane wave experiences the transverse Kerr effect The transverse Kerr effect states that if the reflection plane of the light is perpendicular to the magnetization of the metal the absorption by the metal is different for two opposite directions of the magnetization Therefore the plane wave experiences different absorption for opposite propagation directions The optical isolation of the amplifier covered by ferromagnetic metal can be calculated by solving Maxwells equations for multilayer structure As an example of the waveguide isolator operating at a wavelength of 790 nm we consider a GaAs09P01Al03Ga07As quantum-well (QW) optical amplifier covered by a Co layer (Fig 12) To reduce the absorption by the Co layer a buffer layer of p-Al07Ga03As is inserted between the absorbing Co layer and GaAs09P01Al03Ga07As QW amplifying core layer The optical field of a waveguide mode exponentially penetrates through the buffer layer into the Co layer

n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ

magneto-optic Co layer

amplifying core layer

07

07

03

03

03

07GaAs P Al Ga As QW03 0709 01

Fig 12 GaAsPAlGaAs optical amplifier covered by Co

Figure 13 shows the dependence of the optical lossgain for the forward and backward propagating modes as a function of internal gain of the GaAs09P01 active layer Depending

1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm

internal gain of active layer

Fig 13 Waveguide lossgain as a function of the internal gain of GaAs09P01 active layer (ZaetsampAndo 1999)

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on the value of the internal gain the waveguide can operate as a non-reciprocal amplifier (internal gain gt1680 cm-1) or as a non-reciprocal absorber (internal gain lt1560 cm-1) or as an isolator (1560 cm-1gt internal gain gt1680 cm-1) The isolation ratio is almost constant against internal gain and it is about 180 dBcm Because the waveguide mode interacts with the MO Co layer by its exponential tale through the buffer layer the non-reciprocal lossgain depends on the thickness of the buffer layer Figure 14 shows a dependence of the isolation ratio and the internal gain of GaAs09P01 active layer as function of the thickness of the p-Al07Ga03 As buffer layer when the value of loss for the mode propagating in forward direction is kept to be zero The thinner the buffer layer is the larger isolation ratio can be obtained although the higher amplification is necessary to compensate the loss

300 4000

100

200

cm-1

nm

isol

atio

n

thickness of buffer layer

0

1000

dBcm


Fig 14 Isolation ratio and the required internal gain of GaAs09P01 active layer vs thickness of p-Al07Ga03As buffer layer The lossgain of the mode propagating in forward direction is fixed to be zero (ZaetsampAndo 1999)

Figure 15 compares isolation ratio of structure of Fig12 with Co Fe and Ni cover layer Wavelength dependence of optical constants of Co Fe and Ni are taken into account while

500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength

Fig 15 Isolation ration vs wavelength Wavelength dependence of optical constants of Co Fe and Ni are taken into account while optical constants of amplifier is assumed to be independent on wavelength

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optical constants of amplifier are assumed to be independent of wavelength Among these materials the cobalt is the most suitable for the proposed isolator The isolation ratio only slightly changes vs wavelength Therefore the wavelength dependence of the isolator is determined only by the bandwidth of the amplifier The proposed design of the isolator does not require the periodical reverse of magnetization or the phase matching between TE and TM modes or the interferometer structure It provides the high isolation ratio in a wide range of the internal gain The isolation ratio is proportional to the isolator length These all merits make this design suitable for the monolithical integration of optical isolator with optoelectronic devices It should be noted that MO materials (ferromagnetic metals magnetic semiconductors and magnetic garnets) show the highest values of the MO effect in a wavelength region where they show large absorption Thus the combination of the absorbing MO materials with the optical amplifiers is a viable way to achieve smaller sizes of non-reciprocal devices which is suitable for integrated circuits For the experimental verification of the effect of non-reciprocal loss we fabricated passive optical waveguides covered by a ferromagnetic metal The directional dependence of absorption by the metal is a reason for the isolation in this structure The optical gain in the isolator is used only to compensate the loss To avoid side effects due to the optical amplification we studied a passive waveguide covered by a ferromagnetic metal Two identical waveguides were fabricated where only the material of buffer layer between Co layer and waveguide core was different Figure 16(a) shows the structure of a Ga1-xAlxAs waveguide covered by Co with SiO2 buffer layer and Fig 16 (b) shows the waveguide with AlGaAs buffer layer The Ga1-xAlxAs waveguide was grown with molecular-beam-epitaxy (MBE) on a GaAs (001) substrate Following a 2500-nm-thick Ga055Al045As clad layer and a 900-nm-thick Ga07Al03As core layer a buffer layer of 12-nm-thick SiO2 or 120-nm-thick Ga055Al045As was grown The 10-μm-wide 600-nm-deep rib waveguide was wet etched A 100 nm of Co layer and a 100 nm of Au layer were deposited on the buffer layer A protection layer of 100-nm-thick SiO2 with 8-μm-wide window was used to avoid light absorption at the sidewalls of the waveguide

GaAs substratecladcoreAlGaAs

AuCo

GaAs substratecladcore

SiO 2

AuCo

H

light

side protection

xy

z

a)b)

Fig 16 AlGaAs optical waveguide covered with Co Either a) SiO2 or b) Al045Ga055As was used as the buffer layer Waveguide light propagates in the core layer and slightly penetrates into the Co layer

For the evaluation of non-reciprocal loss laser light (λ=770 nm) was coupled into the waveguide with a polarization-maintaining fiber The output light was detected by a CCD camera A polarizer was placed in front of the CCD camera The magnetic field was applied

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perpendicularly to the light propagation direction and in the film plane with an electromagnet Figure 17 shows the transmission coefficient of TM mode as a function of applied magnetic field for the waveguide with SiO2 buffer and the waveguide with Ga055Al045As buffer A clear hysteresis loop of the transmission coefficient was observed with a coercive force of 35 Oe The transmission coefficient of TE mode showed no dependence on the magnetic field The magnetization curve measured by a superconducting quantum interface device (SQUID) For both samples magnetization curve was identical and the coercive force was 35 Oe The observation of the hysteresis loop of the transmission coefficient of TM mode with the same coercive force is that of Co proves the TM mode transmission depends on magnetization of the Co Considering time-inversion symmetry the difference of transmission in the same direction of light propagation for two opposite directions of magnetic field is equal to the difference in transmission for opposite directions of light propagation in one direction of magnetic field Therefore the amplitude of the hysteresis loop of the transmission corresponds to the isolation provided by the waveguide As can be seen from Fig 17 the isolation direction for a waveguide with a SiO2 buffer is different from that for a waveguide with a Ga055Al045As buffer Therefore the isolation direction depends not only on the magnetization direction of the ferromagnetic metal but on the waveguide structure as well

-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)

Fig 17 Optical transmission in 11-mm-long Ga1-xAlxAs optical waveguides covered by Co at λ=770 nm as a function of applied magnetic field a) with SiO2 as the buffer layer and b) with Ga055Al045As as the buffer layer (Zayets ampAndo (2005))

These results can be explained by considering two contributions to the non-reciprocal loss by MCD and Faraday effects We defined the figure-of-merit (FoM) for this isolator as a ratio of the non-reciprocal absorption to the total absorption by the metal The mode propagation constants non-reciprocal loss and FoM were rigorously calculated from a direct solution of Maxwells equations for the planar waveguide In addition both MCD and Faraday contributions to FoM were roughly estimated by estimating the light energy dissipation resulting from each contribution For the waveguide with SiO2 buffer FoM was calculated to be 795 where MCD and magneto-reflectivity contributions were estimated as -801 and 1586 respectively For the waveguide with Ga055Al045As buffer FoM was calculated to be -719 where MCD and Faraday contributions were estimated as -801 and 111

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respectively The sign of the contributions is different The magnitude of the MCD contribution is almost same for both waveguides On the contrary the magnitude of Faraday contribution is significantly different That is a reason that opposite isolation directions were observed in the waveguides with SiO2 and Ga055Al045As buffers For both waveguides the sums of the MCD and Farady contributions are approximately equal to the FoM calculated from the rigorous solution of Maxwell equations Next we verify the isolation in the optical amplifier covered by the ferromagnetic layer Figure 18 (a) showed the fabricated isolator The optical amplifier consists of 8 In046Ga054AsIn026Ga074P tensile strained quantum wells grown on n-InP substrate The p-InP was used as buffer layer and InGaAs as a contact layer The amplifier has maximum amplification at λ=1566 nm Figure 18 (bc) shows the intensity of amplified spontaneous emission (ASE) as a function of applied magnetic field measured at both edges of the isolator when the weak injection current of 10 mA was used At each edge a hysteresis loop was observed for ASE however the polarity of the loop was different It is because there is difference in gain for the light propagating in forward and backward directions in the amplifier

-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm

8 In046Ga054AsInAs026P074 QW

p-InP 220 nm

pp-In039Ga061 As 80 nm

SiO2 SiO2

Co

Au c)

Fig 18 a) InGaAsInAsP optical amplifier with Co contactAmplified spontaneous emission measured b)from left and c) right edge under small 10 mA injection current as a function of applied magnetic field

Optical isolation of 147 dBcm for TE mode was experimentally observed InGaAsPInP optical amplifier at λ=1550 nm in which one sidewall of waveguide was covered by TiO2Fe (Simizu amp Nakano 2004) Optical isolation of 147 dBcm for TM mode at λ=1550 nm was reported for InGaAsPInP covered by MnAs (Amemiya et al2007) and the optical isolation of 99 dBcm for TM mode at λ=1300 nm was reported for AlGaInAsInP optical amplifier covered by CoFe (Van Parys et al 2006) In all these cases to compensate the loss induced by the metal the high injection current of more than 100 mA (current density more than 3 KAcm2) is required The required current is too high for the isolator to be used in practical devices In order to be suitable for integration the injection current for the isolator should be reduced It is only possible if the figure-of-merit for non-reciprocal loss could be increased As we showed above there are two contributions into the non-reciprocal loss Faraday effect and MCD In the case of Fe or Co these contributions have almost the same amplitude and opposite sign The value of Faraday effect is roughly proportional to the real part of off-diagonal element of permittivity tensor of the metal and the value of MCD is roughly proportional to imaginary part of off-diagonal element If some ferromagnetic metal could be found for which mutual signs between imaginary and real part of off-diagonal

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336

tensor element would be different to that of Fe and Co it would make both contributions of the same sign and would significantly enlarge the figure-of-merit for the non-reciprocal loss

4 Spin-photon memory

Photonics devices benefit from unique non-reciprocal properties of magneto-optical materials If the material is ferromagnetic the data can be stored in this material by means of two directions of residual magnetization An ability to memorize data is another unique property of magneto-optical materials and it can be used for new designs of high-speed optical memory Zayets amp Ando (2009) proposed a new type of high-speed optical memory Non-volatile data storage and high-speed operation are major advantages of this memory Figure 19 shows the proposed design The memory consists of micro-sized memory cells integrated on a semiconductor wafer A bit of data is stored by each cell Each cell consists of semiconductor-made photo detector and nanomagnet made of a ferromagnetic metal The nanomagnet has two stable magnetization directions The data is stored as a magnetized direction in the nanomagnet For the data recording the magnetization direction must be reversed by optical pulse The circularly-polarized optical pulse is absorbed in the semiconductor detector creating spin-polarized electrons Under applied voltage these spin polarized electrons are injected from the detector into the nanomagnet The spin transfer torque is a consequence of the transfer of spin angular momentum from a spin-polarized current to the magnetic moment of a nanomagent If the torque is sufficient the magnetization turns and the data is memorized Due to the optical selection rule the spin-polarized electrons can be created only by the circular polarized optical pulse The linear polarized light excites equal amount of electrons of both up and down spins therefore there is no net spin polarization the current injected into nanomagnet is not spin polarized and there is no spin torque

nanomagnet

detectorlight

+

-

R

Fig 19 Design of spin-photon memory ZayetsampAndo (2009)

Figure 20 shows integration of two memory cells and explains principle of high speed recording There are two waveguide inputs One input is for data pulses and one input is for the clock pulse The clock pulse is used to select for recording a single pulse from sequence of the data pulses Polarization of data pulses and clock pulse are linear and mutually orthogonal Optical paths were split that each memory cell is illuminated by the data pulses and the clock pulse The lengths of waveguides are adjusted so that the phase difference between clock and data pulses is λ4 at each memory cell At the first memory cell the clock pulse came at the same time with first data pulse Therefore these two pulses combined into one circularly polarized pulse Since only first pulse is circularly polarized only this pulse

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excites spin polarized electrons changes magnetization and is memorized All other data pulses are linearly polarized they do not excite spin polarized electrons and they have no effect on the magnetization For the second memory cell the clock pulse is slightly delayed relatively to the data pulses and it comes together with second data pulse Only the second pulse is circularly polarized and can be memorized by the second memory cell Therefore each data pulse can be memorized by individual memory cell The closer the pulses can be placed relatively to each other the more data can be transformed through one line and the faster recording speed of memory can be achieved The minimum interval between pulses at which a pulse can be recorded without any influence of nearest pulse determines the recording speed of the memory

data

mem1

clock delay

mem2

Fig 20 The scheme for the integration of memory cells Pulse diagrams explains the method for the high speed recording Zayets amp Ando (2009)

It was shown (Heberle et al 1996) that spin-polarized excitons can by excited by two linearly cross-polarized pulses even the pulses arrived at different time If the exciton dephasing time is longer than the interval between pulses the excitons excited by two pulses can coherently interfere and create spin polarization For the successful demultiplexing by method proposed on Fig 20 the interval between data pulses should be at least longer than electron dephasing time Also the spin polarization created by circularly polarized pulse should not be destroyed by following linear polarized pulses Next we verified the proposed demultiplexing method at the speed of 22 TBitsec For this purpose we studied dynamics of excitation of spin polarized electrons in Si-doped GaAs (n=7x1016 cm-3) at 80o K Figure 21 shows the experimental setup A mode-locked Tisapphire laser (λ=820 nm ) provides 160 fs linearly-polarized pump and probe pulses Polarization of the pump was rotated by a λ2 waveplate and split by polarization beam splitter (PBS) into clock pulse and data pulse of linear and mutually orthogonal polarizations The data pulse was split into two pulses The second data pulse was 165 λ (~450 fs) delayed Clock and data pulses were combined together by another PBS and focused on the sample The linearly polarized probe beam was 100 ps delayed relatively to the pump and focused on the same spot on the sample The spin polarization of electrons excited by pump beam was estimated from Kerr rotation angle of the probe beam The rotation angle of reflected probe beam was measuring by polarizer (P) and photo detector (det) Intensity of each data pulse was 1-10 μJcm2 Intensity of the probe pulse was 10 times smaller The data pulses and clock pulse were phase locked When the clock pulse and one of data pulse nearly coincided the positive and negative angles of Kerr rotation were observed for delays of (n+14)λ and (n-14)λ

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338

respectively When the pulses were away from each other the Kerr rotation was not observed

λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s

Fig 21 Experimental setup for study the recording speed for spin-photon memory

Figure 22 shows spin polarization of the excited electrons as a function of delay between clock pulse and first data pulse For each point the delay length was equal to (n+14)λ where n is an integer The maximum of spin polarization was observed when the clock pulse coincides with first data pulse The spin polarization decreases when the clock pulse is delayed out of the first data pulse and again increases as the clock pulse coincides with the second data pulse Fig 46 clearly shows that the spin polarization excited by the second data pulse can be separately distinguishable from the spin polarization excited by the first data pulse This means that from two closely placed optical data pulses only one pulse can trigger the recording without influence of another pulse The interval between the data pulses is 450 fs It corresponds to the recording speed of 22 TBitsec Notice that the detection of spin polarization was done 100 ps after data pulse arrived This means that the lifetime of the spin polarized electrons is sufficient long to inject the spin polarized electrons into the nanomagnet for the magnetization reversal

-1000 -500 0 500

spin

pol

ariz

atio

n a

u

Delay of clock pulse fs

Fig 22 Spin polarization of electrons excited by combined beam of clock pulse and two data pulse as a function of delay of clock pulse For each point the delay length was (n+14)λ where n is integer Reading of spin polarization was done 100 ps after arrival of pump pulses Zayets amp Ando (2009)

For the memory operating at speed 22 TBitsec the delay of clock pulse between cells (Fig 21) should be 165λ (~450 fs) the initial magnetization of all nanomagnets should be spin

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339

down and the delay of data pulses relatively to the clock pulse should be (14+m165) λ where m is a number of the data pulse As result of Fig 22 in this case in each cell only one data pulse excites spin polarization and memorized there Other data pulses have no influence on spin polarization of that cell In our experiment the shortest interval between the data pulses when the spin polarization excited by each pulse can be individually distinguished is about 450 fs For shorter interval the spin polarization is overlapped and the spin polarization created by preceding data pulse is reduced by next data pulse which is causing overwriting of data of preceding pulse by next pulse in the cell Therefore the memory can not operate at speed faster than 22 TBitsec By these experiments we demonstrated that from sequence of short-interval pulses it is possible to select only a single pulse for excitation of spin polarized electrons That proves high recording speed of this memory For the memory to be fully functional the magnetization reversal by spin polarized photo-excited electrons should be realized It requires injection of sufficient amount of spin-polarized current from detector into the nanomagnet (Slonczewski 1996) Also the time for the injection of the photo current from the detector into nanomagnet need to be adjusted so that it should be enough long to accomplish the magnetization reversal of the nanomagnet but still it should be shorter than electron spin lifetime in the detector The time which takes for the magnetization of nanomagnet to turn between two stable direction is about 500-1000 ps (Krivorotov 2005) There are several semiconductors in which the electron spin lifetime is longer or comparable with that time For example the spin life time is 100 ns in GaAs at T=4 K (Kikkawa amp D D Awschalom 1999 ) and 100 ps at room temperature (RT) (Hohage et al 2006) 10 ns in GaAsAlGaAs quantum well (QW) at RT (Adachi et al 2001) and several ns in ZnSe QW at RT (Kikkawa et al1997) For the design of Fig 19 the photo current injected in nanomagnet decays with time constant where C is capacity of detector and R is resistance of close loop The should be comparable with magnetization reversal time of the nanomagnet and smaller than the spin life time in the detector To estimate the energy of optical pulse required for magnetization reversal we assumed that τRC is 500 ps the efficiency of photon to spin conversion is 40 and the critical current for the magnetization reversal is 5 mA (Kubota et al 2005) To generate such current the required energy of optical pulse should be about 3 pJ It is in the range of the pulse energies which typically used in case of all-optical switching Therefore the memory may be suitable for the use in present optical communication systems Figure 23 shows the multiplexing scheme for this memory For each memory cell the optical waveguide passes under the nonomagnet Due to the effect of non-reciprocal loss the absorption of light in waveguide will be different for two opposite magnetization directions of the nanomagnet The mode-locked laser which could be integrated on the chip provides the short pulses The waveguide path is split so that a pulse is split and it illuminates every memory cell At output all waveguide paths are combined Each path has different length so that each pulse reaches the output with a different delay and the amplitude of the pulse corresponded to the magnetization of each cell Therefore at the output the serial train of pulses will form with intensities proportional to the data stored in each memory cell This memory is compact integratable compatible with present semiconductor technology and it has fast operation speed If realized it will advance data processing and computing technology towards faster operation speed

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340

data out

clock out

mode-lockedlaser

delay

polarization converter

mem1 mem2

delay

mem3

Fig 23 Multiplexing scheme for spin-photon memory

5 Conclusion

We have demonstrated that magneto-optical materials are important for optoelectronics because of their unique non-reciprocal and memory properties At present there is an industrial demand for a waveguide-type optical isolator and a high-speed non-volatile optical memory The use of magneto-optical materials is unavoidable for the fabrication of these devices

6 Acknowledgement

This work was supported by NEDO We thank R Akimoto Y Suzuki S Yuasa H Saito J-C Le Breton H Kubota A Fukushima and K Yakushiji and V Ganzha for helpful discussions C Debnath for the development of (CdMn)Te waveguide isolator and K Moriyama for technical assistance

7 References

T Adachi Y Ohno F Matsukura ampH Ohno (2001) Spin relaxation in n-modulation doped GaAsAlGaAs (1 1 0) quantum wells Physica E vol 10 36-39 2001

T Amemiya H Shimizu M Yokoyama P N Hai M Tanaka amp Y Nakano (2007) 154-μm TM-mode waveguide optical isolator based onthe nonreciprocal-loss phenomenon device design to reduce insertion loss Applied Optics vol 46 No 23 5784 Aug 2007

K Ando T Okoshi and N Koshizuka (1988) ldquoWaveguide magneto-optic isolator fabricated by laser annealingrdquo Applied Physics Letters Vol 53 4-6 1988

LM Augustin R Hanfoug R JJGJ van der Tol WJM de Laat amp MK Smit (2007) ldquoA Compact Integrated Polarization SplitterConverter in InGaAsPndashInPrdquo IEEE Photonics Technology Letters Vol 19 No 17 1286 ndash 1288 Sept 2007

C BrooksPE Jessop H Deng DO Yevick G Tarr (2006) Passive silicon-on-insulator polarization-rotating waveguides Optical Engineering Vol 45 No 4 044603 2006

M C Debnath V Zayets amp K Ando (2007) (CdMn)Te(CdZn)Te quantum-well waveguide optical isolator with wide wavelength operational bandwidth Applied Physics Letters vol 91 No4 043502 July 2007

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341

H Fukuda KYamada T Tsuchizawa T WatanabeH Shinojima amp S Itabashi (2006) Ultrasmall polarization splitter based on silicon wire waveguides Optics Express Vol 14 No 25 12401 Dec 2006

J K Furdyna (1988) Diluted Magnetic Semiconductors Journal of Appled Physics vol 64 R29- R64 1988

A P Heberle J J Baumberg E Binder T Kuhn K Kohler amp K Ploog (1996) Coherent Control of Exciton Density and Spin IEEE Journal of Selected Topics in Quantum Electronics vol 2 No3 769-775 Sep1996

P E Hohage G Bacher D Reuter amp A D Wieck (2006) Coherent spin oscillations in bulk GaAs at room temperature Applied Physics Letters vol 89 No 23 231101 Dec 2006

JZ Huang R Scarmozzino G Nagy MJ Steel RM Osgood (2000) Realization of a compact and single-mode optical passive polarization converter IEEE Photonics Technology Letters Vol 12 No 3 317-319 Mar 2000

J M Kikkawa amp D D Awschalom (1999) Resonant Spin Amplification in n-Type GaAs Physics Review Letters vol 80 No19 4313-4316 May 1999

J M Kikkawa I P Smorchkova N Samarth amp D D Awschalom (1997) Room-Temperature Spin Memory in Two-Dimensional Electron Gases Science 277 1284-1287 Aug 1997

SH Kim R Takei Y Shoji amp T Mizumoto (2009) Single-trench waveguide TE-TM mode converter OPTICS EXPRESS vol 17 No 14 11267-11273 Jul2009

I N Krivorotov N C Emley J C Sankey S I Kiselev D C Ralph amp R A Buhrman (2005) Time-Domain Measurements of Nanomagnet Dynamics Driven by Spin-Transfer Torques Science vol 307 228-231 Jan 2005

H Kubota A Fukushima Y Ootani S Yuasa K Ando H Maehara K Tsunekawa D D Djayaprawira N Watanabe amp Y Suzuki (2005) Evaluation of Spin-Transfer Switching in CoFeBMgOCoFeB Magnetic Tunnel Junctions Japanese Journal of

Applied Physics Vol 44 No 40 2005 pp L 1237ndashL 1240 Sep 2005 K Onodera T Masumoto amp M Kimura (1994) 980 nm compact optical isolators using

Cdsub 1-x-yMnsub xHgsub yTe single crystals for high power pumping laser diodes Electronics Letters Vol 30 1954- 1955 1994

J C Slonczewski (1996) Current-driven excitation of magnetic multilayers Journal of Magnetism and Magnetic Materials vol 159 L1-L7 1996

H Shimizu ampY Nakano (2004) ldquoFirst demonstration of TE mode nonreciprocal propagation in an InGaAsP_InP active waveguide for an integratable optical isolatorrdquo Japanese Journal of Applied Physics Part 2 vol 43 L1561-L1563 Nov 2004

W Van ParysB Moeyersoon D Van Thourhout R Baets M VanwolleghemBDagens J Decobert O Le Gouezigou D Make RVanheertum amp L Lagae (2006) Transverse magnetic mode nonreciprocal propagation in an amplifying AlGaInAsInP optical waveguide isolator Applied Physics Letters vol88 No7 071115 Feb 2006

H Yokoi T Mizumoto T Takano amp N Shinjo (1999) ldquoDemonstration of an optical isolator by use of a nonreciprocal phase shiftrdquo Applied Optics vol38 7409-7413 1999

W Zaets K Watanabe amp K Ando (1997) ldquoCdMnTe magneto-optical waveguide integrated on GaAs substraterdquo Applied Physics Letters vol 70 No 19 2508-2510 Mar 1997

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W Zaets amp K Ando (1999) ldquoOptical waveguide isolator based on non-reciprocal lossgain of amplifier covered by ferromagnetic layerrdquo IEEE Photonics Technology Letters vol 11 No8 1012-1014 Aug 1999

W Zaets amp K Ando (2000) Magneto-optical mode conversion in Cd1-xMnxTe waveguide on GaAs substrate Applied Physics Letters vol 77 No 11 1593- 1595 Sep 2000

W Zaets amp K Ando (2001) Magnetically Programmable Bistable Laser Diode With Ferromagnetic Layer IEEE Photonics Technology Letters vol 113 No3 185-187 Mar 2001

V Zayets M C Debnath amp K Ando (2004) Complete magneto-optical waveguide mode conversion in Cd 1-xMnxTe waveguide on GaAs substrate Applied Physics Letters vol 84 No 4 565- 567 Jan 2004

VZayets amp K Ando (2005) Isolation effect in ferromagnetic-metalsemiconductor hybrid optical waveguide Applied Physics Letters vol 86 No 26 261105 June 2005

V Zayets amp KAndo (2009) High-speed switching of spin polarization for proposed spin-photon memory Applied Physics Letters vol 94 vol12 121104 Mar 2009 Reprinted with permission from American Institute of Physics Copyright 2004 2005 2007 2009 American Institute of Physics

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Frontiers in Guided Wave Optics and OptoelectronicsEdited by Bishnu Pal

ISBN 978-953-7619-82-4Hard cover 674 pagesPublisher InTechPublished online 01 February 2010Published in print edition February 2010

InTech EuropeUniversity Campus STeP Ri Slavka Krautzeka 83A 51000 Rijeka Croatia Phone +385 (51) 770 447 Fax +385 (51) 686 166wwwintechopencom

InTech ChinaUnit 405 Office Block Hotel Equatorial Shanghai No65 Yan An Road (West) Shanghai 200040 China

Phone +86-21-62489820 Fax +86-21-62489821

As the editor I feel extremely happy to present to the readers such a rich collection of chapters authoredco-authored by a large number of experts from around the world covering the broad field of guided wave opticsand optoelectronics Most of the chapters are state-of-the-art on respective topics or areas that are emergingSeveral authors narrated technological challenges in a lucid manner which was possible because of individualexpertise of the authors in their own subject specialties I have no doubt that this book will be useful tograduate students teachers researchers and practicing engineers and technologists and that they would loveto have it on their book shelves for ready reference at any time

How to referenceIn order to correctly reference this scholarly work feel free to copy and paste the following

Vadym Zayets and Koji Ando (2010) Magneto-Optical Devices for Optical Integrated Circuits Frontiers inGuided Wave Optics and Optoelectronics Bishnu Pal (Ed) ISBN 978-953-7619-82-4 InTech Available fromhttpwwwintechopencombooksfrontiers-in-guided-wave-optics-and-optoelectronicsmagneto-optical-devices-for-optical-integrated-circuits

copy 2010 The Author(s) Licensee IntechOpen This chapter is distributedunder the terms of the Creative Commons Attribution-NonCommercial-ShareAlike-30 License which permits use distribution and reproduction fornon-commercial purposes provided the original is properly cited andderivative works building on this content are distributed under the samelicense


322

We proposed the non-volatile high-speed optical memory which utilizes the magnetization reversal of nanomagnet by spin-polarized photo-excited electrons It was demonstrated experimentally that one selected pulse from a train of two optical data pulses with interval of 450 fs can solely excite the spin-polarized electrons without a disturbance from the unselected optical data pulse (Zayets amp Ando 2009) This proves feasibility for proposed memory to record data train with rate of 22 TBitsec

2 Cd1-xMnxTe waveguide optical isolator

The conventional bulk-type optical isolator consists of a 45-degree Faraday rotator placed between two polarizers [Fig1] The angle between axes of entrance polarizer and exit polarizer is 45 degrees In forward direction the polarization of light is 45 degree rotated by the Faraday rotator to be along the axis of the exit polarizer Therefore the light can pass through the isolator in forward direction In backward direction the direction of polarization rotation is opposite to that in forward direction due the non-reciprocal nature of the magneto-optical effect At the entrance polarizer the polarization is 90 degrees to the polarizer axis and the light is fully blocked

45deg45deg 45deg45deg

45deg45deg45deg45deg90deg

0deg0deg

Fig 1 Design of free-space optical isolator The Faraday rotator is placed between entrance polarizer (left side) and exit polarizer (right side) Upper diagrams show polarization in forward direction Lower diagrams show polarization in backward direction

In present optical networks ferrimagnetic garnet oxide crystals such as Y3Fe5O12 (YIG) and (GdBi)3Fe5Ob are used as magneto-optical materials for discrete optical isolators Because most of the active optical elements (such as the laser diode optical amplifier modulator and optical gate) are produced on GaAs or InP substrates it is desirable to integrate monolithically all optical components on these types of substrate but integration of the isolator is a difficult task Waveguide optical isolator based on the garnet film has been reported (Ando et al 1988) But the garnet-made isolators have not been monolithically integrated with semiconductor optoelectronic devices because these oxide crystals can not be grown on semiconductor substrates Paramagnetic semiconductor Cd1-xMnxTe is promising as a magneto-optical material for integrated optical isolators and circulators Cd1-xMnxTe shares the zinc-blende crystal structure with the typical semiconductor optoelectronic materials such as GaAs and InP thus its film can be grown directly on GaAs and InP substrates Cd1-xMnxTe also exhibits a huge Faraday effect (its Verdet constant is typically 50-200 degcmkG) (Furdyna 1988) near its absorption edge because of the anomalously strong exchange interaction between the sp-band electrons and the localized d-electrons of Mn2+ Furthermore the tunability of its absorption edge from 156 to 21 eV with Mn concentration makes the Cd1-xMnxTe magneto-optical waveguide compatible with (AlGaIn)PGaAs optoelectronic devices operating in the wavelength range of 600-800 nm For longer-wavelength (λ=800-1600 nm)

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Laserbeam

GaPprism

Polarizer

GaAs

Cd Mn Te1-x x

TV-CAMERAH





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TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

ty


0

25

50

75

100

Nor

mol

azed

int

ensi

ty

TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

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0

25

50

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Nor

mol

azed

int

ensi

ty



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325



Buffer ZnTe (10 nm)








Co

re



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(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG



740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW


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0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


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TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






323


Laserbeam

GaPprism

Polarizer

GaAs

Cd Mn Te1-x x

TV-CAMERAH





wwwintechopencom


324


TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

ty


0

25

50

75

100

Nor

mol

azed

int

ensi

ty

TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

ty


0

25

50

75

100

Nor

mol

azed

int

ensi

ty



wwwintechopencom


325



Buffer ZnTe (10 nm)








Co

re



wwwintechopencom


326


(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG



740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW


wwwintechopencom


327

0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


wwwintechopencom


328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






324


TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

ty


0

25

50

75

100

Nor

mol

azed

int

ensi

ty

TM

TE


b)

c)

d)

e)

f)

0 2 4 6 80

25

50

75

100

Nor

mol

azed

int

ensi

ty


0

25

50

75

100

Nor

mol

azed

int

ensi

ty



wwwintechopencom


325



Buffer ZnTe (10 nm)








Co

re



wwwintechopencom


326


(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG



740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW


wwwintechopencom


327

0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


wwwintechopencom


328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






325



Buffer ZnTe (10 nm)








Co

re



wwwintechopencom


326


(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG



740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW


wwwintechopencom


327

0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


wwwintechopencom


328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






326


(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG

(a)

λ = 710 nm

λ=785 nmλ=760 nm

(b)H=55

kG

H=55

kG

2

mm

with

QW

(c) (d)

without

QW 2

mm

λ=760 nm λ=785 nm

H=55

kG

H=55

kG



740 750 760 770 780 7900

500

1000

1500

2000

2500

H = 55 kG

Wavelength λ (nm)

Far

aday

rot

atio

n Θ F

(deg

cm

)

with QW without QW


wwwintechopencom


327

0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


wwwintechopencom


328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






327

0 25 50 75 1000

5

10

15

20

25


Well width (Aring)

Wave

length

rang

e (

nm

)

of

isola

tion r

atio


Wav

elen

gth

rang

e (n

m)

ofco

mpl

ete

mod

e co

nver

sion

0 25 50 75 100

0

10

20

30

isolation 27 dB



reciprocalrotator


wwwintechopencom


328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






328

TM1

port 1

port 2 port 4

port 3

TM2

TM2

TE2

TE1

TM1

TE1

TE2



TMTE TM

TMTM

TM

TE

TE

TE TM

TE

TE TM

TE

TM

TE


input

absorber

outputport 3

port 4

port 1

port 2

45 degreereciprocal

rotator



wwwintechopencom


329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






329



wwwintechopencom


330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






330


k

E

M

EM

k

x

z

y

x

z



metal

core

TM mode

a)b)



( )~ zi k z t

E e c cωminus +f

and 0zE = (1)


x

y

Ei

E= plusmn (2)




(3)


( 0yE = ) we have


x z

z x

E ki

E k= (4)


wwwintechopencom


331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






331


n-GaAs substrate

p-Al Ga As 250 nm

n-Al Ga As 1 mμ



07

07

03

03

03




1500 1600 1700

-200

0

200

cm-1

backward

forward

gain

los

s

dBcm



wwwintechopencom


332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






332


300 4000

100

200

cm-1

nm

isol

atio

n


0

1000

dBcm




500 600 700 8000

100

200

dBcm

Ni

FeCo

nm

iso

latio

n

wavelength


wwwintechopencom


333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






333



AuCo


SiO 2

AuCo

H

light

side protection

xy

z

a)b)



wwwintechopencom


334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






334


-150 -100 -50 0 50 100 150

-330

-327

-324

-321

-318

Tra

nsm

issi

on d

B

Magnetic Field Oe

SiO2 buffer

-150 -100 -50 0 50 100 150

-372

-368

-364

-360

Tra

nsm

issi

on d

B

Magnetic Field Oe

AlGaAs buffer

(a) (b)



wwwintechopencom


335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






335


-150 -100 -50 0 50 100 150

475

480

485

490

495

AS

E i

nten

sity

nW

Magnetic Field Oe

I=10 mA

-150 -100 -50 0 50 100 150450

455

460

465

470

475

480

485

I=10 mA

AS

E i

nten

sity

nW

Magnetic Field Oe

a) b)

n-InP substrate

n-InP 300 nm


p-InP 220 nm


SiO2 SiO2

Co

Au c)



wwwintechopencom


336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






336




nanomagnet

detectorlight

+

-

R



wwwintechopencom


337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






337


data

mem1

clock delay

mem2



wwwintechopencom


338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






338


λ2

Delaypr

obe

data pulses

clock pulse

pump

PBS PBS

laser

Pdet

Delay

GaA

s



-1000 -500 0 500

spin

pol

ariz

atio

n a

u




wwwintechopencom


339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






339


wwwintechopencom


340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






340

data out

clock out

mode-lockedlaser

delay


mem1 mem2

delay

mem3


5 Conclusion


6 Acknowledgement


7 References







wwwintechopencom


341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






341


















wwwintechopencom


342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821






342







wwwintechopencom





Phone +86-21-62489820 Fax +86-21-62489821









Phone +86-21-62489820 Fax +86-21-62489821





Magneto-optical Devices for Optical Integrated Circuits

Documents

Transcript of Magneto-optical Devices for Optical Integrated Circuits